Measuring time to fusion as a means of determining degree of parallel activation of the heart

Abstract

A method for determining the degree of parallel activation of a heart undergoing pacing includes calculating vectorcardiogram (VCG), or electrocardiogram (ECG), or electrogram (EGM) waveforms from right ventricular pacing (RVp) and left ventricular pacing (LVp). A synthetic biventricular pacing (BIVP) waveform is generated by summing the VCG of the RVp and LVp, or by summing the ECG of the RVp and the LVp, or by summing the EGM of the RVp and the LVp. A corresponding EGM or ECG or VCG waveform from real BIVP is calculated. The method includes comparing the synthetic BIVP waveform and the real BIVP waveform and calculating time to fusion by determining the point in time in which the activation from RVp and LVp meets and the synthetic and the real BIVP curves start to deviate. A delay in time to fusion indicates a higher degree of parallel activation.

1 . A method for determining the degree of parallel activation of a heart undergoing pacing, the method comprising:
 calculating a vectorcardiogram, VCG, or electrocardiogram, ECG, or electrocardiogram, ECG, waveforms from right ventricular pacing, RVp, and left ventricular pacing and/or multisite pacing or multipoint pacing, LVp;   generating a synthetic biventricular pacing, BIVP, waveform pacing by summing the VCG of the RVp and the LVp, or by summing the ECG of the RVp and the LVp, or by summing the ECG of the RVp and the LVp;   calculating a corresponding EGM or ECG or VCG waveform from real BIVP;   comparing the synthetic BIVP waveform and the real BIVP waveform;   calculating time to fusion by determining the point in time in which the activation from RVp and LVp meets and the synthetic and the real BIVP curves start to deviate;   wherein   a delay in time to fusion indicates that a larger amount of tissue is activated before wave fronts for electrical activation meet, thereby indicating a higher degree of parallel activation.   
     
     
         2 . The method of  claim 1 , wherein the calculated time to fusion is a first time to fusion, the method further comprising:
 providing pacing through an additional electrode;   calculating a second VCG or ECG or EGM waveforms from RVp, and LVp, the RVp and LVp being pacing including the additional electrode;   generating a second synthetic BIVP waveform pacing by summing the second VCG of the RVp and the LVp, or by summing the second ECG of the RVp and the LVp, or by summing the second EGM of the RVp and the LVp;   calculating a corresponding second EGM, ECG or VCG waveform from real BIVP, the BIVP being pacing including the additional electrode;   comparing the second synthetic BIVP waveform and the second real BIVP waveform;   calculating second time to fusion by determining the point in time in which the activation from RVp and LVp meets and the second synthetic and the second real BIVP curves start to deviate; and   comparing the first time to fusion and the second time to fusion.   
     
     
         3 . The method of  claim 1 , wherein the step of measuring time to fusion representing electrical activation of the heart further comprises:
 measuring surface biopotentials of the patient to produce an electrocardiogram, ECG;   determining the reference time from the point of onset, offset or the full duration of a QRS signal measured from the ECG; and   determining the duration of the QRS complex; and wherein the step of comparing the time to fusion with the duration of electrical activation of the heart further comprises:   comparing the first time delay of time to fusion with the duration of the QRS complex; and if the first time delay relative to the QRS complex is longer than the second time delay relative to the QRS complex, then identifying the presence of more parallel activation with the first time.   
     
     
         4 . The method of  claim 2 , wherein, if the second time to fusion is less than the first time to fusion, then
 determining that there is no benefit of pacing from the additional electrode.   
     
     
         5 . The method of  claim 1 , wherein the calculated time to fusion is a first time to fusion, the method further comprising:
 providing pacing through at least one electrode at a different position;   calculating a third VCG, or ECG, or EGM, waveforms from RVp, and LVp, the RVp and LVp being pacing including the at least one electrode at a different position;   generating a third synthetic BIVP waveform pacing by summing the third VCG of the RVp and the LVp, or by summing the third ECG of the RVp and the LVp, or by summing the third EGM of the RVp and the LVp;   calculating a corresponding third EGM or ECG or VCG waveform from real BIVP, the BIVP being pacing including the at least one electrode at a different position;   comparing the third synthetic BIVP waveform and the third real BIVP waveform;   calculating third time to fusion by determining the point in time in which the activation from RVp and LVp meets and the third synthetic and the third real BIVP curves start to deviate; and   comparing the first time to fusion and the third time to fusion.   
     
     
         6 . The method of  claim 5 , further comprising;
 selecting the electrode positions corresponding to the longest time to fusion for further pacing.   
     
     
         7 . The method of  claim 1 , wherein the step of calculating of VCG(s) or ECG(s) or EGM(s) further comprises;
 receiving data from electrodes implanted in the patient.   
     
     
         8 . The method of  claim 1 , wherein the step of calculating of VCG(s) or ECG(s) or EGM(s) further comprises;
 receiving data from surface electrodes on the patient;   extrapolate a map of electrical activation onto the heart; and   calculating an inverse solution EGM or ECG or VCG waveform.   
     
     
         9 . The method of  claim 1 , comprising identifying reversible cardiac dyssynchrony of a patient by detecting a shortening of a delay to onset of myocardial synergy, using measurements of an event resulting from the onset of myocardial synergy, via a method comprising:
 calculating a first time delay between the event resulting from the onset of myocardial synergy and a reference time by:   using data received from one or more sensor(s) to measure the time of an event resulting from the onset of myocardial synergy;   processing signals from the same sensor(s), or one or more other sensor of the one or more sensor(s), to determine the first time delay between the measured time of the event resulting from the onset of myocardial synergy and the reference time;   measuring biopotentials representing electrical activation of the heart; comparing the first time delay between the measured time of the event resulting from the onset of myocardial synergy and the reference time with the duration of electrical activation of the heart; and   if the first time delay is longer than a set fraction of electrical activation of the heart, then identifying the presence of cardiac dyssynchrony in the patient;   applying pacing to the heart of the patient;   calculating a second time delay between the event resulting from the onset of myocardial synergy following pacing and the reference time following pacing by:   using the at least one sensor to measure the event resulting from the onset of myocardial synergy following pacing; and   processing signals from the one or more sensor(s) to determine the second time delay between the determined time of the event resulting from the onset of myocardial synergy and the reference time following pacing; comparing the first time delay and the second time delay; and if the second time delay is shorter than the first time delay, then identifying the presence of reversible cardiac dyssynchrony in the patient.   
     
     
         10 . The method of  claim 1 , comprising determining optimal electrode number and positions for cardiac resynchronization therapy on a heart of a patient, via a method comprising;
 generating a 3D mesh of at least part of the heart from a 3D model of at least part of the heart of the patient, the 3D mesh of at least a part of the heart comprising a plurality of nodes;   aligning the 3D mesh of at least part of a heart to images of the heart of the patient;   placing additional nodes onto the 3d mesh corresponding to a location of at least two electrodes on the patient;   calculating a propagation velocity of the electrical activation between the nodes of the 3D mesh corresponding to the location of the at least two electrodes; extrapolating the propagation velocity to all of the nodes of the 3D mesh; calculating the degree of parallel activation of the myocardium for each node of the 3D mesh; and   determining the optimal electrode number and position on the heart of the patient based on the node(s) of the 3D mesh with a calculated degree of parallel activation of the myocardium above a predetermined threshold.   
     
     
         11 . The method of  claim 1 , comprising:
 comparing the synthetic BIVP and real BIVP waveform when applying pacing from a number of electrodes; calculating time to fusion;   adding one electrode;   calculating new time to fusion;   comparing the first with the second;   if adding an electrode does not change time to fusion this indicates that the added electrode activates areas before fusion occurs, thereby indicating a higher degree of parallel activation.   
     
     
         12 . The method of  claim 11  utilizing multidimensional VCG or ECG or EGM. 
     
     
         13 . The method of  claim 1  utilizing surface ECG or EGM from pacing electrodes instead of VCG. 
     
     
         14 . The method of  claim 1  including compensating for a delay in stimulus to QRS onset; suggesting an offset between stimuli; pacing with the new offset; generating both synthetic and real BIVP curves with offset; generating a new time to fusion with a RV to LV offset (VV-delay, ventricle to ventricle delay). 
     
     
         15 . A system for determining the degree of parallel activation of a heart undergoing pacing, the system comprising;
 one or more sensor(s) to measure biopotentials;   one or more electrodes for providing pacing;   a data processing module configured to:
 calculate a vectorcardiogram, VCG, or electrocardiogram, ECG, or electrocardiogram, EGM, waveforms from right ventricular pacing, RVp, and left ventricular pacing, LVp from the measured; 
 generate a synthetic biventricular pacing, BIVP, waveform pacing by summing the VCG of the RVp and the LVp, or by summing the ECG of the RVp and the LVp, or by summing the EGM of the RVp and the LVp; 
 calculate a corresponding EGM or ECG or VCG waveform from real BIVP; compare the synthetic BIVP waveform and the real BIVP waveform; 
 calculate time to fusion by determining the point in time in which the activation from RVp and LVp meets and the synthetic and the real BIVP curves start to deviate; wherein 
 a delay in time to fusion indicates that a larger amount of tissue is activated before wave fronts for electrical activation meet, thereby indicating a higher degree of parallel activation. 
   
     
     
         16 . A computer programme product containing instructions that, when executed, will configure a computer system to carry out the method of  claim 1 .